Composition comprising rubbery halogenated copolymer and a comminuted metal and process of vulcanizing same



COMPOSITION COMPRISING RUBBERY HALO- GENATED COPOLYMER AND A COMMINU'I'ED METAL AND PROCESS OF VULCANIZING SAME Leon S. Minckler, Jr., Metnchen, Delmer L. Cattle, Highland Park, and Lawrence T. Eby, Linden, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Feb. 14, 1957, Ser. No. 640,064

13 Claims. (Cl. 260-415) No Drawing.

This invention relates to rubbery polymeric compositions which are halogenated copolymers of isoolefins and multiolefins and to the preparation and vulcanization of such compositions and more particularly to improved methods for curing halogenated butyl rubber with minor proportions of comminuted tin and/ or zinc.

Copolymers of the above general type, especially Where the copolymer contains about 85 to 99.5% (preferably about 95 to 99.5%) of a C to C isoolefin such as isobutylene with about 15 to 0.5% (preferably 5. to 0.5 weight percent) of a multiolelin of about 4 to 14, pref erably about 4 to 6 carbon atoms and having a Staudinger molecular weight of between about 20,000 and 300,000, are commonly referred to in patents and literature as butyl rubber or GR-I rubber (Government Rubber- Isobutylene) and, for example, is referred to as butyl rubber in textbook Synthetic Rubber by G. S. Whitby. The preparation of butyl type rubber is described in U.S. Patent 2,356,128 to Thomas et al. as well as in technical literature. In general, the multiolefinic component of the rubber comprises a conjugated diolefin such as isoprene, butadiene, dimethyl butadiene, piperylene, etc. The reaction product of isobutylene and isoprene is preferred. Butyl rubber has a mole percent unsatnration of between about 0.5 to 15.0. t

Halogenated butyl-type rubbery copolymers, which are vulcanizable with zinc oxide and covulcanizable with more highly unsaturated rubbers, are produced by halogenating the butyl rubber in a manner which-does not degrade the molecular weight thereof, but halogenated sufiiciently to produce a rubbery product which when vulcanized retains its tensile strength upon heat aging. Such halogenated butyl rubbers are readily covulcanizable with more highly unsaturated rubbers with or without added sulfur to produce rubbery products for excellent heat aging resistance. The chlorinated butyl rubbers so formed also do not greatly differ in curing rate as compared to natural rubber and synthetic rubbers such as GR-S rubber.

It has now been discovered that halogenated butyl rubber may be cured with comminuted or powdered metallic tin and/r zinc to produce vulcanizates having improved tensile strength compared to zinc oxide cured vulcanizates without significantly altering the modulus or elongation.

Inpracticing the present invention, 100 parts by Weight of halogenated butyl rubber are compounded with about 20 to 100 parts by weight of a filler such as clays or carbon blacks, and about 2 to 30, advantageously about 3 to 20 parts by weight of comminuted tin and/or zinc with the optional addition of such conventional compounding agents as antioxidants such as p-amino betanaphthylamine, sulfur, sulfur-containing accelerators, quinoid compounds, antitack agents such as stearic acid or zinc stearate, resins, plasticizers, etc. The resulting compounded stock is then cured. by heating the same for about 1 minute to 5 hours, preferably for about minutes to 2 hours at a temperature level of between about 250 a 2,941,975 Patented June. 21, 196.0

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to 400 F. and preferably at about 275 to .375" F. to produce a vulcanizate having excellent tensile strength.

In producing halogenated butyl rubber to be vulcanized in accordance with the present invention, unmodified, unvulcanized butyl rubber is carefully halogenated so as to contain about at least 0.5 weight percent (preferably at least about 1.0 weight percent) combined halogen but not more than about X weight percent combined chlorine or 3 X weight percent combined bromine wherein:

and

L=mole percent of the multiolefin in the polymer M zrnolecular weight of the isoolefin M =molecular weight of the multiolefin M =atomic weight of chlorine or bromine Restated, there should be at least about 0.5 weight percent of combined halogen in the polymer but not more than about one atom of chlorine or 3 atoms of bromine combined in the polymer per molecule of multiolefin present therein: i.e. not more than about one atom of combined chlorine or three atoms of combined bromine per double bond in the polymer.

Suitablehalogenating agents which may be employed are gaseous chlorine, liquid bromine, alkali metal hypochlorites, sodium hypobromite, C to C tertiary alkyl hypochlorites or hypobromites, sulfur chlorides or bromides (particularly oxygenated sulfur chlorides or bromides), pyridinium chloride perchloricle, N-bromosuccinimide, iodine monochloride, alphachloroacetoacetanilide, tri-bromophenol bromide, N-chl-oroacetamide, beta bromo-methyl phthalirnide, N,N'-dimethyl-5,5-dichloro or dibromo hydantoin, and other common halogenating agents.

'Ihe halogenation is generally conducted at above 0 to about +l00 C., advantageously at about 0 to 65 C., preferably at about 20 to 50 C. (room temperature being satisfactory), depending upon the particular halogenation agent, for about one minute to several hours. An advantageous pressure range is from about 0.5 to 400 p.s.i.a.; atmospheric pressure being satisfactory. The halogenation conditions are regulated to halogenate the rubbery copolymer to the extent above-mentioned.

The halogenation may be accomplished in various ways. One process comprises preparing a solution of the copolymer as above, in a suitable inert liquid organic solvent such as a C to C or preferably a C to C inert hydrocarbon or halogenated derivatives of saturated hydrocarbons, examples of which are hexane, heptane, naphtha, mineral spirits, cyclohexane, alkyl substituted cycloparafiins, benzene, chlorobenzene, chloroform, trichloroethane, carbon tetrachloride, mixtures thereof, etc., and adding thereto gaseous chlorine, liquid bromine, or

other halogenating agent, which may optionally be in solution, such as dissolved in any inert hydrocarbon, an alkyl chloride, carbon tetrachloride, etc.

The concentration of the butyl rubber in the solvent will depend upon the type of reactor, molecular weight The resulting halogenated butyl rubber polymer may be recovered in various manners. The polymer may be precipitated with acetone or any other known non-solvent for the butyl rubber and dried under about 1 to 760 millimeters or higher of mercury pressure absolute at about to 180 C., preferably at about 50 to 150 C. (e.g. 70 C.). Other methods of recovering the halogenated butylrubber polymer from the hydrocarbon solution of the. same are by conventional spray or drum drying techniques. Alternatively the halogenated butyl rubber-containing solution may be injected into a vessel containing agitated Water heated to a temperature sufficient to flash off the hydrocarbon solvent and form an aqueous slurry of the halogenated butyl rubber. The halogenated butyl rubber may then be separated from this slurry by filtration, dried and recovered as a crum or as a dense sheet or slab by conventional milling and/or extruding procedures. The halogenated copolymer formed advantageously has a viscosity average molecular weight between about 200,000 and 1,500,000 and a mole percent unsaturation of between about 0.5 to 15.0, preferably about 0.6 to 5.0.

In order to more fully illustrate the present invention, the following evperimental data are given:

CHLORINATED BUTYL RUBBER A A copolymer of about 97% isobutylene and 3% isoprene having a viscosity average molecular weight of 320,- 000 was dissolved in hexane to form a solution. To this polymer solution, a weight percent (based on the polymer) of liquid sulfu ryl chloride as the chlorinating agent was added and reacted for 30 minutes with the polymer at room temperature. The resulting chlorinated copolymer was precipitated with acetone, collected and redissolved in hexane three times and ultimately dried and analyzed and found to have a viscosity average molecular weight of 320,000 and to contain 1.4% chlorine based on the polymer. The' physical characteristics of both zinc oxide and diamine-cured vulcanizates, containing this chlorinated interpolymer, were excellent.

CHLORINATED RUBBERS B TO L Other examples of halogenated isoolefin-multiolefin copolymers which can be used are tabulated hereinafter, the amount of isoolefin and multiolefin in copolymer, halogenation agent, and amount of halogen combined in the copolymer being as follows:

chlorine was added to the reactor through the conduit via the sparger ring. The chlorination was then terminated and the solution containing the chlorinated butyl rubber formed was agitated for an additional 20 minutes.

. Composition Pounds of chlorinated Product (percent) Butyl rubber 170 98. Benzene solvent 1,540 Chlorine 4.8 (Le. 2.8%)- 1.35

The resulting water-washed solution containing the stabilized, chlorinated butyl rubber M was then recovered by injecting the solution into an agitated aqueous slurry containing zinc stearate and a small amount of a non-ionic wetting gent of the aliphatic polyoxyethylene ether type (e.g. Sterox A] or Tergitol NPX) in an amount of 0.7 pound of the zinc stearate per 100 pounds of chlorinated butyl rubber as a dispersing aid. The agitated solution was maintained at a temperature between about 190 and 210 F. (e.g., 200 F.) whereby to flash off the benzene solvent and form an aqueous slurry of the chlorinated butyl rubber in water. This slurry was then: filtered and the chlorinated butyl rubber, which was in the form of a wet crumb, was placed in a Proctor and Schwartz tray drier maintained at 180 F. (i.e. 82 C.) and dried for 12 hours. The crumb depth on thetray was about /2 inch. The crumb was then completely dried and compacted by milling for 15 minutes on. aconventional rubber mill having a roll temperature of 260 F. (i.e. 127 C.).

Example One hundred parts by weight of chlorinated butyl rubber M were compounded on a cold mill (e.g. 20 C.) with 50 parts by weight of MPC carbon black, 1 part by weight of zinc stearate, 0.2 part by weight of phenyl Halogenated (Percent) Rubber Isoolefin (Percent) 1 Multiolefin (Percent) 1 Halogenation Agent Halogen 1n the Rubber 1 Isobutylene (98). Isoprene (2) S0201; chlorine. Isobutylene (95) Oh in G014 chlorine;

Isobutylene (94).

C1 in G014 C12 in GU14 Isobutylene (92) Myrcene (8 0)... chlorine 2-methyl-butene-1 (95) Isoprene (5) C12 n Hexane-. 1 5 chlor ne. 3-methyl-butene-l (96) Butadiene (4) Clzlll Hexane 1.9 chlor ne. Isobutylene (98) l vinyl cyclohexene-3 (2) C12 in G014 0.8 chlor ne. Isobutylene (02L. Butadiene (8) gaseous chlor ne 2.8 chlor ne. Isobutylene (85) Isoprene (l5) gaseous chlorine 6.6 chlor ne. Isobutylene (98).. Isoprene (2) N, N- lichl0ro-5, 5-di- 1.1chlor1ne.

methyl hydantoin. Isobutylene (98) Isoprene (2) Liquid bromine 2.3 bromine.

1 N orE.(Percent) in all instances is percent by weight.

CHLORINATED' BUTYL RUBBER M An additional run was made chlorinating a commercial 6 butyl rubber dissolved in'benzene. The butyl rubber had a Mooney viscosity at 212 F. for 8 minutes of 75, and a mole percent unsaturation of 1.6. The chlorination of a solution of the uncured butyl rubber was conducted in a 500-gallon glass-lined Pfaudler reactor equipped with an agitator, bafile, submersed stainless steel sparger ring and a conduit leading into the ring.

Gaseous chlorine was. continuously added to the butyl rubber solution over a period of /2 hour at a temperature level of 30 C. and under atmospheric pressure. The

Vulcanizing Agent Powdered Powdered Zine Zine Tin Oxide Modulus at 3e0% Elong. (p.s.i.) 68.; 650 695 Tensile Strength (p.s.i.) l, 518 l, 515 1,375 Elongation (percent) 500 535 500 An additional run was made with the tin-compounded stock in which the vulcanization was for 120 minutes at 307 F. with a resulting tensile strength of 1675 p.s.i.

The above data show that powdered tin or zinc cures chlorinated butyl rubber into a vulcanizate having an improved tensile strength compared to a vulcanizate cured by zinc oxide.

Resort may be had to various modifications and variations of the disclosed embodiments without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. A composition comprising 100 parts by weight of a rubbery halogenated copolymer of about 85 to 99.5 weight percent of a C to C isoolefin and about to 0.5 weight percent of a C to C multiolefin and about 2 to 30 parts by weight of a comminuted metal selected from the group consisting of tin, zinc, and mixtures thereof, the degree of halogenation of said copolymer being such that it contains at least 0.5 weight percent of a combined halogen selected from the group consisting of chlorine and bromine, said copolymer containing at most three atoms of combined halogen per double bond in the copolymer.

2. A composition according to claim 1 which the halogenated copolymer contains at least 0.5 weight percent chlorine but not more than about one atom of chlorine per double bond in the copolymer.

3. A composition according to claim 1 in which the halogenated copolymer contains at least about 0.5 weight percent bromine but not more than about three combined atoms of bromine per double bond in the copolymer.

4. A composition according to claim 1 in which the comminuted metal is 5. A composition according to claim 1 in which the comminuted metal is zinc.

6. A composition according to claim 1 which has been vulcanized by heating the same for between about 1 minute and 5 hours at a temperature level of between about 250 and 400 F. to produce a vuloanizate having a high tensile strength.

7. A composition comprising 100 parts by weight of a rubbery polymer having a viscosity average molecular weight of at least about 200,000 comprising atoms of hydrogen, carbon and a halogen selected from the group consisting of bromine, chlorine, iodine and mixtures thereof, containing in its structure a major proportion of hydrocarbon units derived by the copolymerization of isoolefins containing about 4 to 7 carbon atoms with multiolefins of about 4 to 14 carbon atoms and also containing suflicient units in which a pair of carbon atoms is linked by an olefinic double bond that the mole percent unsaturation is between about 0.5 and 15; said polymer containing at least about 0.5 weight percent halogen but not more than about one combined atom of halogen per double bond in the polymer; said polymer being in composition with a vulcanizing amount of about 2 to 30 parts by weight of a comminuted metal selected from the group consisting of tin, zinc, and mixtures thereof.

8. A composition according to claim 7 in which the polymer contains chlorine.

9. A composition according to claim 7 in which the polymer contains bromine.

10. A composition according to claim 7 in which the comminuted metal is present in an amount of between about 2 and 20 weight percent based on the halogencontaining polymer.

11. A process which comprises vulcanizing halogenated butyl rubber in the presence of about 2.0 and 30.0 weight percent of a comminuted metal selected from the group consisting of tin, zinc, and mixtures thereof at a temperature level of between about 250 and 400 F. for a time between about 1 minute and .5 hours until the resulting vulcanizate exhibits a tensile strength of at least about 1500 p.s.i., the combined halogen in said butyl rubber being selected from the group consisting of chlorine and bromine, and the degree of halogenation being such that the halogenated butyl rubber contains at least 0.5 weight percent of combined halogen but at most one atom of chlorine per double bond in the rubber where chlorine is the combined halogen, and at most three atoms of combined halogen per double bond in the polymer where bromine is the combined halogen, said butyl rubber being a copolymer of about to 99.5 Weight percent of a C to C isoolefin and about 15 to 0.5 weight percent of a C to C multiolefin.

12. A composition comprising 100 parts by weight of a rubbery chlorinated copolymer of about to 99.5% of isobutylene and about 5 to 0.5% of isoprene, said chlorinated copolymer containing at least 0.5% chlorine but not more than about one atom of chlorine per double bond in the copolymer, admixed with about 3 to 20 parts by weight of comminuted tin, said tin being the sole curative present. t

13. A process which comprises vulcanizing parts by weight of chlorinated butyl rubber in the presence of about 3 to 20 parts by weight of comminuted tin, at a temperature of about 275 to 375 F. for about 10 minutes to 2 hours, until the resulting vulcanizate exhibits a tensile strength of at least about 1500 p.s.i., said chlorinated butyl rubber containing at least 0.5% chlorine but not more than about one atom of chlorine per double bond in the copolymer, said butyl rubber being a copolymer of about 85 to 99.5 weight percent of a C to C isoolefin and about 15 to 0.5 weight percent of a C to C multiolefin.

References Cited in the file of this patent UNITED STATES PATENTS 2,441,945 Frolich et al. May 25, 1948 2,631,984 Crawford et a1. Mar. 17, 1953 2,732,354 Morrissey et al. Jan. 24, 1956 FOREIGN PATENTS 158,769 Australia Apr. 24, 1952 

1. A COMPOSITION COMPRISING 100 PARTS BY WEIGHT OF A RUBBER HALOGENATED COOLYMER OF ABOUT 85 TO 99.5 WEIGHT PERCENT OF A C4 TO C7 ISOOLEFIN AND ABOUT 15 TO 0.5 WEIGHT PERCENT OF A C4 TO C14 MULTIOLEFIN AND ABOUT 2 TO 30 PARTS WEIGHT OF A COMMINUTED METAL SELECTED FROM THE GROUP CONSISTING OF TIN, ZINC, AND MIXTURES THEREOF, THE DEGREE OF HALOGENATION OF SAID COPOLYMER BEING SUCH THAT IT CONTAINS AT LEAST 0.5 WEIGHT PERCENT OF A COMBINED HALOGEN SELECTED FROM THE GROUP CONSISTING OF CHLORINE AND BROMINE, SAID COPOLYMER CONTAINING AT MOST THREE ATOMS OF COMBINED HALOGEN PER DOUBLE BOND IN THE COPOLYMER. 